Envelope feeders are typically used by organizations such as banks or insurance companies, print shops, and mailing houses that service such organizations, to produce a large volume of mail pieces. For example, banks send out monthly balance ledgers, insurance companies send out claim summaries, and for corporations shareholders might receive quarterly income/dividend statements. Each envelope must be labeled in order to properly utilize the U.S. Postal System, and each must meet certain USPS printing positional requirements. While in the past “windowed” envelopes were utilized in order that preprinted envelopes might be combined with individually printed sheets of paper oriented to show through the envelope window, most modern mail printing systems include the ability to individually print envelopes using on-site, relatively inexpensive laser or inkjet printers. This allows for the combining of customized envelopes with customized printed sheets at the point of disembarkation.
However, the feeding of envelopes into relatively inexpensive commercial laser or inkjet printers can be problematic. The typical configuration is to have an “envelope stacker” or “envelope shoe” holding dozens or even hundreds of envelopes in a stacked column from which individual envelopes are pulled from the bottom of the stack and conveyed along a conveyor deck that is positioned to feed envelopes into the manual feed tray of a printer. A pair of friction rollers commonly referred to as “footballs” presses down upon a leading edge of an envelope held in the stacker and in conjunction with a pair of conveyor rolling belts engages the envelope to sheer it away from the bottom of the envelope stack. The footballs include removable donut weights on a spindle that extends upward from the feed deck so that the pressure of the footballs may be adjusted in response to envelope size and thickness, and other conditions. Alternatively, the footballs are biased downwards with a spring which may be adjusted with a tensioning knob or screw. The sheered envelope then moves forward under the weight of additional passive rollers on the conveying rollers to keep consistent friction between each envelope and the conveyor so that the envelopes maintain edge alignment relative to a receiving input or ingestion area on a printer, such as a manual input tray.
However, these “stacker” based envelope feeders are operator intensive because a myriad of elements require continuing adjustment and attention by an operator. First, the footballs must be made with a consistent friction coefficient and, hence, the material diopter must be closely monitored during manufacturing. Second, the weight of envelopes changes with the envelope stack height and consistent sheering of envelopes can typically be maintained only for a certain range of envelope stack height which may vary with each new batch of envelopes. In addition, adjustments to the side walls and backstop retaining wall in the envelope stacker must be adjusted for a particular weight and size of envelope. Finally, as conveyor belt friction varies with time, and due to variations in humidity, dust, and other environmental factors, football weight, position of the footballs relative to the leading edge of an envelope, and the backstop wall angle must be adjusted frequently in order to provide a consistent feeding of envelopes into the input tray or slot of a printer. Hence, an operator must become accustomed to each feeder and skilled at making minute adjustments to the feeder elements to keep a consistent flow of envelopes into a printer.
The issue affects more than just print job speed completion. Modern laser printers are designed for high printing speeds and the processing of large batches of stock media. Often such systems apply toner images to a transfer belt and roller in anticipation of receiving a fast moving group of media sheets. Printers have sensors at their source input channels and if a few envelopes are processed and then the next expected envelope does not appear in an expected time interval a “stall” condition occurs within the printer and the transfer belt and roller may need to be cleaned and reprocessed in order to prepare for the arrival of a new batch of envelopes. Hence, great amounts of toner may be wasted and the life expectance of a printer's transfer roller may also be decreased. The problem is exacerbated in color laser printers.
Hence, what is needed is an envelope feeder that will work with relatively inexpensive inkjet or laser printers and keep those printers continuously fed or “primed” with envelopes without stalls, and without the constant and continuous operator attention required by conventional envelope feeders.